The present invention relates generally to tracking radar systems and specifically to a tracking servo compensator that permits switching from over track to point track and from one tracked target to another without undesirable transients that could cause loss of track.
A tracking radar system measures the coordinates of a target and provides data which may be used to determine the target path and predict the future position. All or part of the available radar data range, elevation angle, original angle and doppler shaft may be used in predicting the future position of the target.
In conventional radar systems, the antenna beam is positioned by a servomechanism which mechanically steers the radar tracking beam by physically moving the antenna. A limitation on the tracking accuracy of the radar system is the hunting action of the servomechanism. The task to the servomechanism is sufficiently severe in maintaining track on a moving target while handling the backlash and compliance in the gears, shafts and structure of the mount which mechanically steers the radar tracking beam by physically moving the antenna.
The task of providing accurate tracking through the use of a servomechanism in radar tracking systems is alleviated, to some degree, by the following patents: U.S. Pat. No. 2,715,776 issued to Knowles et al on Aug. 22, 1955; U.S. Pat. N0. 4,034,208 issued to Vaeth et al on July 5, 1977; U.S. Pat. No. 3,443,476 issued to Heider et al on May 13, 1969; U.S. Pat. No. 3,829,659 issued to Margolis on Aug. 13, 1974; U.S. Pat. No. 2,658,677 issued to Lundstrom et al on Nov. 10, 1953; U.S. Pat. No. 4,148,026 issued to Gendreu on April 3, 1979.
Knowles et al is pertinent for its disclosure of a fire control and tracking apparatus for unstable craft such as aircraft or ships. The patent speaks of rate aided tracking and of aided tracking in which a predetermined displacement of the tracking control member produces both a corresponding proportional angular displacement of the line of sight and angular rate of change of the line of sight. The device of the patent also includes means for slewing the line of sight of the system. An angular acceleration aided electro-optical target tracking system is disclosed in Vaeth et al. Heider et al is directed to a gun control system having a movable platform and a movable gun sight mounted on the platform. A movable platform and sight uses integrated angular velocity signals to help track a target in the Margolis patent. Gandrew tracks a moving target from a moving platform and Lundstrom et al disclose a regenerative tracking apparatus.
The task of the servomechanism is compounded when the users of the radar system command the radar to switch targets or switch from area to point tracking. However, some of the prior art references disclose a method for providing smooth controlled-speed transitions between track points during mode switching.
In view of the foregoing discussion, it is apparent that there currently exists the need for an improved tracking servo compensator that permits switching from area to point track and from one tracked target to another with controlled speed to prevent undesirable transients that could cause loss of track. The present invention is directed towards satisfying that need.